Effects of a High-Concentration LiPF 6 -Based Carbonate Ester Electrolyte for the Electrochemical Performance of a High-Voltage Layered LiN i0.6 Co 0.2 Mn 0.2 O 2 Cathode

作者：Qi Liu, Hongliang Xu, Feng Wu, Daobin Mu, Lili Shi, Lei Wang, Jiaying Bi, Borong Wu · 发表于：ACS Applied Energy Materials · 年份：2019 · DOI：10.1021/acsaem.9b01917 · 被引用次数：30 · 研究领域：Advancements in Battery Materials、Advanced Battery Materials and Technologies、Advanced Battery Technologies Research

Lithium-ion battery electrolytes are key components contributing to the Li + transference and the formation of solid electrolyte interface (SEI) film. A high-concentration LiPF 6 -based EC/DMC electrolyte is employed to investigate the electrochemical performance of layered LiNi 0.6 Co 0.2 Mn 0.2 O 2 cathode material at the high voltage of 4.6 V. Cyclic voltammetry tests indicate that the 6.5 M EC/DMC-LiPF 6 high-concentration electrolyte enjoys a stronger oxidation resistance compared with 1 M diluted electrolyte. It is indicated that the highest occupied molecular orbital (HOMO) energy of nEC-Li + and nDMC-Li + solvation complexes is reduced with the Li + concentration increase, suggesting that the high Li + concentration enhances the oxidation resistance of the solvent molecules by the density functional theory (DFT) method. X-ray photoelectron spectroscopy (XPS) tests demonstrate that the SEI film is different from that of the diluted electrolyte on the cathode surface by using the high-concentration electrolyte. The composite cathode of LiNi 0.6 Co 0.2 Mn 0.2 O 2 exhibits a 161.3 mAh/g reversible capacity at the rate of 0.2C (1C = 180 mA g –1 ) after 100 cycles by using the high-concentration electrolyte, while a 138.6 mAh/g lower capacity is exhibited in the diluted electrolyte. The improvement of cycling performance should be attributed to the prevention of the interface side reactions on the cathode.